Scouting

Recently, I have heard about a game where someone has lost his catapult to enemy towers because he blindly ran into them. This should never happen; even if you are in a hurry (e. g. if you have to destroy a wonder in time), you should use scouts to check the enemy town for towers and other defenses.

Stone Age

The first scouting is done before placing the Town Center. Make sure you find a good spot, but do not waste too much time searching either. Then you start building up and eventually get your first military forces, the Clubmen. You should then assign a number to each Clubman (CTRL+1 to 9) and spread them into different directions. Look for more resources (mainly all sorts of food). After you have found some additional resources, do not go too far anymore - your village could be attacked while your Clubmen are taking a walk :)

Scouting the sea with fishing boats is pointless, you had better get them some fish. The exploration of the sea will have to wait.

At the beginning, artifacts are free scouts and work fairly well:

"When available, use those artifacts as scouts. After your first 16 villagers are doing what you want them to be doing and
you are just waiting on that Age upgrade, drive this cute little Ark of the Covenant cart about. It will change colors on
you when an enemy unit (not building) moves nearby. A free, rather fast moving scout that will tell you right away if there
are enemies nearby."

Bazooka

Tool Age

Here you get the real Scout. He is fast and sees very far, thus being the perfect unit to eliminate all black spots in the minimap. Make sure that you build your Stables soon after the Archery, give each Scout his own number and continue as described above. You should be able to locate the nearest enemies on land maps. If you find an enemy town, do not try to kill his villagers with the Scout - the Scout is weak and has a different AI that makes him a bad attacker. Since Scouts are pretty expensive, make sure you use them well. Then three or four of them will be enough.

At sea, the Scout ship is the only war ship you can get, and get it quickly! Try to find more fish and other islands. Do not attack an enemy fleet with one ship. After you have found enemy ships, it is time to assemble all war ships in one group. Seperating one ship for more scouting is ok, but do not divide your fleet into pieces anymore. If you find an enemy town, get two transports ready with an invasion force. Scout ships do not do much damage against buildings. Concentrate on the enemy troops and villagers.

Bronze and Iron Age

Here the fights are getting hectic. You should finish exploring the map in the early Bronze Age. Do not forget to scout the enemy town before you attack! Some players stop scouting after the map is explored, do not do that! If you find a spot with a lot of resources, build a tower there to watch over it. Then you will know when someone tries to get them.

At sea, before moving your fleet to a new spot, take a single war ship to check whether the coast is clear.

Waypoints

This feature is very useful for scouting. Instead of just right clicking at the destination, you hold SHIFT while clicking with the right mouse button. A flag will appear, marking that waypoint. You can set more waypoints like this. To mark the destination, just right click after releasing SHIFT. The picture shows such a waypoint in an unexplored area.

Conclusion

Good scouting will prevent you from losing troops needlessly and therefore always pays off. Do not forget that the Scout is a weak attacker and should not be used against villagers - that's the job of your Cavalry units. Scouts do make good catapult killers, though :)